In Part 1 of this series we saw that even if one gives credence to the oft-repeated but flawed estimates from the World Health Organization of the present-day contribution of climate change to global mortality, other factors contribute many times more to the global death toll. For example, hunger’s contribution is over twenty times larger, unsafe water’s is ten times greater, and malaria’s is six times larger. With respect to ecological factors, habitat conversion continues to be the single largest demonstrated threat to species and biodiversity. Thus climate change is not the most important problem facing today’s population.

In Part 2 we saw that even if we assume that the world follows the IPCC’s warmest (A1FI) scenario that the UK’s Hadley Center projects will increase average global temperature by 4°C between 1990 and 2085, climate change will at most contribute about 10% of the cumulative death toll from hunger, malaria and flooding into the foreseeable future. It would simultaneously reduce the net population at risk of water stress.

Clearly, climate change would, through the foreseeable future, be a bit-player with respect to human well-being.

Here I’ll examine whether, notwithstanding that climate change is likely to be outranked by other factors when it comes to human well-being, whether it is likely to be the most important global ecological problem if not today, at least in the foreseeable future.

As in Part 2, I’ll rely on estimates of the global impacts of climate change from the British-government sponsored “Fast Track Assessments” (FTAs).

The following figure, which presents the FTA’s estimates of habitat converted to cropland as of 2100, shows that the amount of habitat lost to cropland may well be least under the richest-but-warmest scenario (A1FI), but higher under the cooler (B1 and B2) scenarios. Thus, under the warmest scenario, despite a population increase cropland could decline from 11.6% in the base year (1990) to less than half that (5.0%) in 2100: Climate change may well relieve today’s largest threat to species and biodiversity!

One reason for this result is that higher atmospheric concentrations of CO₂ might make agriculture more efficient, and this productivity increase would not have been vitiated as of 2100 by any detrimental impacts of higher temperatures.

The next figure shows that in 2085 non-climate-change related factors will dominate the global loss of coastal wetlands between 1990 and 2085.

[In this figure, SLR = sea level rise. Note that the losses due to SLR and “other causes” are not additive, because a parcel of wetland can only be lost once. For detailed sources, see here.]

Thus we see that neither on grounds of public health nor on ecological factors is climate change likely to be the most important problem facing the globe this century.

So if you hear anyone make the claim that climate change is the most important environmental problem facing the globe now or whenever, ask to see the analysis that compares climate change with other problems.

In future postings I’ll look at the policy implications of the results from the FTA in greater detail.